Been doing a bit more research about this strange issue with auto flash on the Ricoh GRD IV and I have sort of come up with a solution - use manual flash!
Luckily the flash is very easy to configure without having to go into the menu system. I can even assign one of the function keys to give direct access to the manual flash power level.
I have found that 1/64 power generally seems fine for fill flash. A benefit of using manual flash is that you do not get those annoying pre-flashes that auto flash generates. These pre flashes tend to make some people blink and certainly if you ever need to take a flash photo of an animal, then manual flash is the way to go as animals seem to have a fast blink reflex.
Here is an example - I had tried taking pictures with auto flash and every shot had made the cat blink, but manual flash does not cause any blinks as there is only a single flash fired, and at 1/64 power we are probably talking of 1/10000s duration, so far to fast to cause blinking.
I'm still quite impressed with Darktable, and the way it helps organise collections of images - I remember working with UFraw and this seems a lot better. Another thing I remember is that after shooting film for a while then going back to digital is that you end up with a lot of images that need organising. It is also important to "cull" a lot of images to keep numbers managable.